Lithium ion secondary batteries have advantages such as high energy density, low self-discharge, excellent long-term reliability and the like, and therefore they have been put into practical use in notebook-type personal computers, mobile phones and the like. Furthermore, in recent years, in addition to high functionality of electronic devices, by expansion of the market for motor-driven vehicles such as electric vehicles and hybrid vehicles, and acceleration of development of home and industrial power storage systems, development of a high performance lithium ion secondary battery which is excellent in battery characteristics such as cycle characteristics and storage characteristics and further improved in capacity and energy density is demanded.
As a negative electrode active material providing a high capacity lithium ion secondary battery, metal-based active materials such as silicon, tin, alloys thereof, and metal oxides thereof have attracted attention. For example, Patent Document 1 describes a lithium ion secondary battery comprising a negative electrode containing amorphous silicon and graphite particles. Patent Document 2 describes a secondary battery having a negative electrode comprising a negative electrode active material containing silicon or the like and graphite, and specifically describes a secondary battery comprising crystalline Si particles having an average particle size of 5 μm and graphite particles having an average particle diameter of 10 μm is disclosed. Patent Document 3 discloses an active material layer comprising carbon material particles capable of absorbing and desorbing lithium ions, metal particles capable of alloying with lithium such as silicon, and oxide particles capable of absorbing and desorbing lithium ions.